Process for fabricating bump electrode

ABSTRACT

A method forwarding a semiconductor device that is excellent in bonding strength of bumps with respective protruded electrodes and having high reliability. A wiring pattern  28  to be connected to an electrode  22  of a semiconductor chip  20  is formed on an insulting film  23  formed on the semiconductor chip  20  in which the electrode  20  is formed. Protruded electrodes  32  are formed on the wiring pattern  28 . The wiring pattern  28  is covered with a protective film  36 , and a bump  38  for external connection is formed on the end portion of each of the protruded electrodes  32  exposed from the protective film  36 . The bump  38  is formed in such a manner that the bump is bonded to the at least entire end face of each of the protruded electrodes  32.

This application is a division of Ser. No. 09/464,232 filed Dec. 15,1999 now U.S. Pat. No. 6,198,169.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device, having achip-size package structure, and a process for producing the same.

2. Description of the Related Art

A process for producing semiconductor devices comprising assemblingsemiconductor devices in the wafering step has been developed (JapaneseUnexamined Patent Publication (Kokai) No. 10-79362). The process canprovide semiconductor devices each having a separate chip-size packagestructure completed by cutting, and reduce the production costs.

The production process comprises forming a wiring pattern (rewiringpattern), to be connected to electrodes of the semiconductor chip, on aninsulating film formed on the semiconductor chip, forming protrudedelectrodes by plating the wiring pattern, forming a protective filmcovering the wiring pattern by compression molding, and forming a solderbump for external connection on the end portion of each of the protrudedelectrodes.

The step of forming a protective film comprises the followingprocedures.

That is, a top face and a bottom face are heated to about 175° C. Atemporary film is absorbed by the top face.

A wafer on which a wiring pattern and protruded electrodes are formed isplaced on the bottom face, and a sealing resin is placed on the wafer.

The resin is melted by the heat and pressure of the sealing mold to bespread over the entire wafer, and held within the mold to be cured.

The wafer is taken out of the mold, and the temporary film is peeledoff.

A solder bump for external connection is formed on the end portion ofeach of the protruded electrodes.

However, the conventional process for producing a semiconductor devicehas been found to have the following problems.

That is, when the process is carried out by compression molding whereina resin is placed on a wafer, the resin is melted by pressing the resinwith a mold, and the molten resin is spread over the entire wafer toform a protective film, the protective film is also placed on the endface of each of the protruded electrodes, and removal of the protectivefilm from the end face becomes incomplete.

Accordingly, when a solder bump 12 is bonded to the end portion of aprotruded electrode 10 as shown in FIG. 16, the bond area of the solderbump 12 is reduced by a protective film 14, and the bond strengthbecomes insufficient, which causes a problem in reliability.

Moreover, the bonded portion of the solder bump 12 makes an acute anglewith the surface of the protruded electrode 10, which causes the problemthat the bump tends to be easily removed by impact.

In addition, the reference numerals 15, 16 and 18 designate asemiconductor chip, an insulating film formed from a polyimide resin anda rewiring pattern formed on the insulating film 16, respectively.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a semiconductor devicewhich is excellent in the bond strength of a bump with each of theprotruded electrodes and which is highly reliable, and a process forproducing the same.

In a semiconductor device according to the present invention wherein awiring pattern to be connected to an electrode of a semiconductor chipis formed on an insulating film formed on the semiconductor chip surfaceon which the electrode is formed, protruded electrodes are formed on thewiring pattern, the wiring pattern is covered with a protective film,and a bump for external connection is formed on the end portion of eachof the protruded electrodes. exposed from the protective film, the bumpis formed by bonding the bump to the at least entire end face of each ofthe protruded electrodes.

Since the bump is bonded to the entire end face of each of the protrudedelectrodes as described above, the bump is excellent in bond strength.

The bump mentioned above is characterized in that a barrier plated layeris formed on the end face of each of the protruded electrodes, and thatthe bump is formed in such a manner that the bump is bonded to theentire barrier plated layer.

Since the bump shows good wettability with the barrier plated layer, itis bonded to the entire barrier plated layer.

The protective film is characterized in that the protective film isformed to have a top surface lower than the position at which the bumpis bonded to each of the protruded electrodes.

Since the top surface of the protective film is lower than that of theprotruded electrodes, the protective film is never placed on the endportion of the protruded electrodes, and the bump is bonded to theentire end face of each of the protruded electrodes.

The protruded electrodes are appropriate when an oxide film is formed onthe peripheral surface of each of the protruded electrodes, and whenthere is a gap between the protective film and the peripheral surface ofeach of the protruded electrodes.

The protruded electrodes thus become independent of the protective film,and are not influenced thereby even when the coefficient of thermalexpansion of the electrodes differs from that of the film. Stressconcentration between the protruded electrode and the bump is thereforerelaxed, and crack formation and the like, in the bump and in theprotective film, can be suppressed.

Furthermore, it is also appropriate in this case to form the protectivefilm in such a manner that the level of the protective film becomeshigher than the position at which the bump is bonded to each of theprotruded electrodes, and that part of the peripheral surface of thebump is contacted with the protective film.

As a result, a gap between each of the electrodes and the protectivefilm can be closed, and invasion of moisture, etc. can be prevented.

Next, in a process for producing a semiconductor device according to thepresent invention wherein a wiring pattern to be connected to anelectrode of a semiconductor chip is formed on an insulating film formedon the semiconductor chip surface on which the electrode is formed,protruded electrodes are formed on the wiring pattern, the wiringpattern is covered with a protective film, and a bump for externalconnection is formed on the end portion of each of the protrudedelectrodes exposed from the protective film, the process comprises thesteps of: covering the wiring pattern formed on the insulating film witha resist layer, and forming holes in the resist layer to expose part ofthe wiring pattern; plating the wiring pattern within the holes to formthe protruded electrodes; removing the resist layer; effecting sealingby supplying a resin to the wiring pattern to form a resin layer havinga top surface lower than that of the protruded electrodes, therebyforming a protective film; and forming a bump on each of the protrudedelectrodes in such a manner that the bump is bonded to the at leastentire end face of each of the protruded electrodes.

Since the protective film is formed by potting or spin coating to have atop surface lower than that of each of the protruded electrodes, theentire end face of each of the protruded electrodes is exposed, and abump is bonded to the entire end face, which improves the bond strengthof the bump.

Moreover, the process is appropriate when the process comprises platingto form a barrier plated layer on the end face of each of the protrudedelectrodes, and when the bump is formed in the bump-forming step in sucha manner that the bump is bonded to the entire barrier plated layer.

Furthermore, in a process for producing a semiconductor device accordingto the present invention wherein a wiring pattern to be connected to anelectrode of a semiconductor chip is formed on an insulating film formedon the semiconductor chip surface on which the electrode is formed,protruded electrodes are formed on the wiring pattern, the wiringpattern is covered with a protective film, and a bump for externalconnection is formed on the end portion of each of the protrudedelectrodes exposed from the protective film, the process comprises thesteps of: covering the wiring pattern formed on the insulating film witha resist layer, and forming holes in the resist layer to expose part ofthe wiring pattern; plating the wiring pattern within the holes to formthe protruded electrodes; removing the resist layer; forming the bump oneach of the protruded electrodes in such a manner that the bump isbonded to the at least entire end face of each of the protrudedelectrodes; and effecting sealing, after forming the bump, by supplyinga resin to the wiring pattern to form a protective film.

Since the protective film is formed after forming bumps, the bumps eachcan be formed at a desired position of the protruded electrode, and thebond strength of the bumps can be increased.

Also in this case, the process is appropriate when the process comprisesthe plating step of forming a barrier plated layer on the end face ofeach of the protruded electrodes, and when the bump is formed in thebump-forming step in such a manner that the bump is bonded to the entirebarrier plated layer.

Furthermore, in a process for producing a semiconductor device accordingto the present invention wherein a wiring pattern to be connected to anelectrode of a semiconductor chip is formed on an insulating film formedon the semiconductor chip surface on which the electrode is formed,protruded electrodes are formed on the wiring pattern, the wiringpattern is covered with a protective film, and a bump for externalconnection is formed on the end portion of each of the protrudedelectrodes exposed from the protective film, the process comprises thesteps of: covering the wiring pattern formed on the insulating film witha resist layer, and forming holes in the resist layer to expose part ofthe wiring pattern; plating the wiring pattern within the holes to formthe protruded electrodes; removing the resist layer; forming the bump oneach of the protruded electrodes in such a manner that the bump isbonded to the at least entire end face of each of the protrudedelectrodes; forming a photosensitive resist layer to cover the wiringpattern and the protruded electrodes; and effecting photolithography byexposing to light and developing the photosensitive resist layer to forma protective film which covers the wiring pattern and to expose theprotruded electrodes.

Since the protective film is formed after forming bumps also in thisprocess, the bumps can be formed without being influenced by theprotective film, and the bond strength of the bumps can be increased.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing the step of forming an insulatingfilm on a wafer;

FIG. 2 is a sectional view showing the step of forming a bonded metallayer and a copper layer on an insulating film;

FIG. 3 is a sectional view showing the step of forming a wiring pattern;

FIG. 4 is a sectional view showing the step of forming a protrudedelectrode;

FIG. 5 is sectional view showing a wafer on which protruded electrodesare formed;

FIG. 6 is a sectional view showing the step of supplying a resin on awafer in a first embodiment;

FIG. 7 is a sectional view showing the shape of a protruded electrode;

FIG. 8 is a sectional view showing bumps bonded to protruded electrodes,respectively;

FIG. 9(a) and FIG. 9(b) are sectional views each showing the form of abonded bump;

FIG. 10 is a sectional view showing bumps bonded to protrudedelectrodes, respectively, in a second embodiment;

FIG. 11 is a sectional view showing the step of supplying a resin on awafer;

FIG. 12 is a sectional view showing the step of forming a photosensitiveresist layer in a third embodiment;

FIG. 13 is a sectional view showing the step of forming a protectivefilm with a photosensitive resist layer;

FIG. 14 is a sectional view showing a gap formed between a protectivefilm and a protruded electrode;

FIG. 15 is a sectional view showing a protrusion formed at the end of aprotruded electrode; and

FIG. 16 is a sectional view showing a bump in the prior art.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Appropriate embodiments of the present invention will be explained belowin detail based on the attached drawings.

Although a process for forming a rewiring pattern on a wafer is known,the process will be briefly explained by making reference to FIG. 1 toFIG. 4.

Firstly, as shown in FIG. 1, an insulating film 23 composed of apolyimide resin is formed on a passivation film 21 of a wafer(semiconductor chip) 20 except for the portion for an aluminum electrode22.

Secondly, as shown in FIG. 2, a bonded metal layer 25 comprising doublelayers of titanium and chromium and a copper layer 26 are formed bysputtering.

Next, as shown in FIG. 3, a resist pattern 27 in which the copper layer26 is exposed in a groove shape in the portion where a wiring pattern(rewiring pattern) is to be formed is formed. A plated film is formed onthe copper layer 26 by electroplating of copper while the resist pattern27 and the copper layer 26 are used as a mask and a conducting layer,respectively, thereby forming a wiring pattern 28.

The resist pattern 27 is removed.

Next, as shown in FIG. 4, a resist layer 30 is formed on the wiringpattern 28, and holes 31 are formed in the resist layer 30 to exposepart of the wiring pattern 28.

The wiring pattern 28 within the holes 31 is electroplated with copperto form protruded electrodes 32.

A barrier plated layer 33 comprising a nickel coating and a gold coatingis further formed on the end face of each of the protruded electrodes32. The barrier plated layer 33 may also comprise two layer coatingsformed with a nickel coating and a palladium coating.

The resist layer 30 is then removed.

The exposed copper layer 26 and the bonded metal layer 25 are removed byetching, thereby isolating the wiring pattern 28.

The wafer 20 on which the insulating film 23, the wiring pattern 28 andthe protruded electrodes 32 have been formed can thus be obtained (FIG.5).

First Embodiment

Next, as shown in FIG. 6, a resin composed of an epoxy resin, etc. issupplied to the wiring pattern 28 from a nozzle 34, flattened, and curedto form a protective film 36. Spin coating is suitable for flatteningthe resin.

The level of the protective film 36 is made lower than that of theprotruded electrodes 32.

Specifically, when the protruded electrodes 32 are formed byelectroplating to make a protrusion, the center of the end face of eachof the electrodes becomes protuberant to some extent as shown in FIG. 7.The protective film 36 is formed in such a manner that the level of thefilm becomes lower than that of the edge portion of the barrier platedlayer 33.

A solder bump 38 is subsequently formed on each of the protrudedelectrodes 32 as shown in FIG. 8.

The solder bump 38 is formed in such a manner that the bump 38 is bondedto the entire barrier plated layer 33 having good wettability (FIG.9(a)). That is, an oxide film is formed on the peripheral surface of theprotruded electrode 32 formed with copper. Since the wettability ofsolder with the oxide film is poor, the solder bump 38 is formed so thatthe bump is bonded to the entire barrier plated layer 33. In addition,when a highly active flux is used, the oxide film on the peripheralsurface of the protruded electrode 32 is, sometimes removed, and thesolder bump 38 adheres to the portion where the oxide film has beenremoved. The state is included in the state where “the bump is bonded tothe entire barrier plated layer 33” in the present invention (FIG.9(b)).

As explained above, since the bump is formed while the bump is bonded tothe entire end face of the protruded electrode 32, in more detail, thebump is bonded to the entire barrier plated layer, a large bond area isobtained, and the bond strength of the bump 38 can be increased.Moreover, the bond angle made by the solder bump 38 with the protrudedelectrode does not become an acute angle; therefore, the solder bump isalso excellent in strength on impact.

In addition, the entire end face of the protruded electrode 32designates the entire end face included within the sectional. area ofthe protruded electrode 32 (within the area of the plan view thereof)even when the end face forms a curved surface.

Second Embodiment

FIG. 10 and FIG. 11 show a second embodiment.

In the present embodiment, the solder bumps 38 are firstly formed on theprotruded electrodes 32, respectively, on the wafer 20 shown in FIG. 5,as shown in FIG. 10.

Similarly to FIG. 9, also in this case, since an oxide film is formed onthe peripheral surface of each of the protruded electrodes 32, theprotruded electrodes show poor wettability with solder; therefore, thesolder bumps 38 are each determined to be bonded to the entire barrierplated layer 33.

Next, as shown in FIG. 11, a resin such as an epoxy resin is suppliedfrom a nozzle 34 to the wiring pattern 28, and cured to form aprotective film 36.

The level of the protective film 36 is arbitrary in this case. That is,since each of the bumps 38 has already been bonded to the protrudedelectrode 32 to form a necessary bond area, the bond strength of thebumps 38 is not influenced by the protective film 38.

Third Embodiment

In the present embodiment, the solder bumps 38 are formed on theprotruded electrodes 32, respectively, as shown in FIG. 10 for thesecond embodiment, and a photosensitive resist layer 40 is formed tocover the wiring pattern 28 and even the top of the solder bumps 38 asshown in FIG. 12.

Next, as shown in FIG. 13, the photosensitive resist layer 40 is exposedand developed by photolithography to form a protective film 42 whichcovers the wiring pattern 28 and to disclose the protruded electrodes32.

A positive photosensitive resist is used for the photosensitive resistlayer 40. Control of the exposure time can control the depth ofexposure, and as a result the thickness of the resist layer, which canbe removed by etching, can be controlled.

Furthermore, since the light does not impinge on a portion near the rootof each of the solder bumps 38, the resist layer covering the peripheryof the bond portion between each of the solder bumps 38 and thecorresponding protruded electrode 32 can be left as shown in FIG. 13,whereby the bond portion can be protected.

The bond strength of the solder bumps 38 can be increased also in thepresent embodiment.

In each of the embodiments mentioned above, each of the semiconductordevices can of course be completed separately by finally cutting thewafer 20.

In addition, semiconductor devices can each be completed separately bycutting the wafer first to give separate semiconductor chips, and thenfollowing the steps as mentioned above.

In the second embodiment, as shown in FIG. 14, a gap (structure withoutadhesion) can be formed between the protective film 36 and theperipheral surface of the protruded electrode 32, depending on the typeof resin used.

That is, as explained above, an oxide film is formed on the peripheralsurface of the protruded electrode 32, and some resins show poorwettability with the protruded electrode when the oxide film is formed.As a result, the protective film 36 does not adhere to the peripheralsurface of the protruded electrode 32.

An oxide film may also be positively formed on the peripheral surface ofthe protruded electrode 32.

Consequently, the protruded electrode 32 becomes independent of theprotective film 36, and is not influenced thereby even when thecoefficient of thermal expansion of the electrode differs from that ofthe film. Stress concentration in the bond portion between the protrudedelectrode 32 and the bump 38 is relaxed, and crack formation, and thelike, in the bond portion can be suppressed.

Also in this case, it is appropriate to form the protective film 36 insuch a manner that its level becomes higher than the position at whichthe bump 38 is bonded to the protruded electrode 32, and that part ofthe peripheral surface of the bump is contacted with the protective film36 (FIG. 14).

As a result, the gap between the protruded electrode 32 and theprotective film 36 can be closed, and invasion of moisture, and thelike, can be prevented.

FIG. 15 shows another embodiment of the end face shape of the protrudedelectrode 32.

In the present embodiment, the end face central portion of the protrudedelectrode 32 has a still more protuberant shape (protruded portion 32a).

In order to form such a protruded portion 32 a, the following procedureis recommended. A split 28 a is adhered to the wiring pattern 28 whenthe protruded electrode 32 is to be formed by plating, and the protrudedelectrode 32 is formed on the wiring pattern 28 including the slip 28 aby plating. Since the plated coating is formed to have an approximatelyuniform thickness, the protruded portion 32 a corresponding to the split28 can be formed.

The split 28 a can be formed by plating during the step of forming thewiring pattern 28.

Formation of such a protruded portion 32 a can increase the end facearea of the protruded electrode 32, which further increases the bondstrength of the bump 38.

The present invention has been explained above in various ways by makingreference to appropriate embodiments. However, the present invention isnot restricted to the embodiments, and many modifications of the presentinvention are naturally possible so long as the modifications do notdepart from the spirit and the scope of the invention.

According to the semiconductor device and the production process of thepresent invention, a semiconductor device excellent in the bond strengthof the bumps can be provided.

What is claimed is:
 1. A process for producing a semiconductor devicewherein a wiring pattern to be connected to an electrode of asemiconductor chip is formed on an insulating film formed on thesemiconductor chip surface on which the electrode is formed, protrudedelectrodes are formed on the wiring pattern, the wiring pattern iscovered with a protective film, and a bump for external connection isformed on the end portion of each of the protruded electrodes exposedfrom the protective film, the process comprising the steps of: coveringthe wiring pattern formed on the insulating film with a resist layer,and forming holes in the resist layer to expose part of the wiringpattern; plating the wiring pattern within the holes to form theprotruded electrodes; removing the resist layer; effecting sealing bysupplying a resin to the wiring pattern to form a resin layer having atop surface lower than that of the protruded electrodes, thereby forminga protective film; and forming the bump on each of the protrudedelectrodes in such a manner that the bump is bonded to the entire endface of each of the protruded electrodes.
 2. The process for producing asemiconductor device according to claim 1, wherein the process comprisesplating to form a plated barrier layer on the end face of each of theprotruded electrodes; and the bump is formed in such a manner that thebump is bonded to the entire plated barrier layer.
 3. A process forproducing a semiconductor device wherein a wiring pattern to beconnected to an electrode of a semiconductor chip is formed on aninsulating film formed on the semiconductor chip surface on which theelectrode is formed, protruded electrodes are formed on the wiringpattern, the wiring pattern is covered with a protective film, and abump for external connection is formed on the end portion of each of theprotruded electrodes exposed from the protective film, the processcomprising the steps of: covering the wiring pattern formed on theinsulating film with a resist layer, and forming holes in the resistlayer to expose part of the wiring pattern; plating the wiring patternwithin the holes to form the protruded electrodes; removing the resistlayer; forming the bump on each of the protruded electrodes in such amanner that the bump is bonded to the entire end face of each of theprotruded electrodes; and effecting sealing, after forming the bump, bysupplying a resin to the wiring pattern to form a protective film. 4.The process for producing a semiconductor device according to claim 3,wherein the process comprises plating to form a plated barrier layer onthe end face of each of the protruded electrodes, and the bump is formedin such a manner that the bump is bonded to the entire plated barrierlayer.
 5. A process for producing a semiconductor device wherein awiring pattern to be connected to an electrode of a semiconductor chipis formed on an insulating film formed on the semiconductor chip inwhich the electrode is formed, the wiring pattern is covered with aprotective film, and a bump for external connection is formed on the endportion of each of the protruded electrodes exposed from the protectivefilm, the process comprising the steps of: covering the wiring patternformed on the insulating film with a resist layer, and forming holes inthe resist layer to expose part of the wiring pattern; plating thewiring pattern within the holes to form the protruded electrodes;removing the resist layer; forming the bump on each of the protrudedelectrodes in such a manner that the bump is bonded to the entire endface of each of the protruded electrodes; forming a photosensitiveresist layer to cover the bump, wiring pattern and the protrudedelectrodes; and effecting photolithography by exposing to light anddeveloping the photosensitive resist layer to form a protective filmwhich covers the wiring pattern and the protruded electrodes and toexpose the bump.
 6. The process for producing a semiconductor deviceaccording to claim 4, wherein the resin layer has a top surface lowerthan that of the edge portion of the plated barrier layer.
 7. Theprocess for producing a semiconductor device according to claim 1,wherein the supplying of the resin to the wiring pattern to form a resinlayer is by spin coating the resin onto the semiconductor device.
 8. Theprocess for producing a semiconductor device according to claim 2,wherein the plated barrier layer comprises a nickel coating and a goldcoating.
 9. The process for producing a semiconductor device accordingto claim 2, wherein the plated barrier layer comprises a nickel coatingand a palladium coating.
 10. The process for producing a semiconductordevice according to claim 1, wherein the bond angle made by the solderbump with the end face does not become an acute angle, thereby providingadditional strength on impact.
 11. The process for producing asemiconductor device according to claim 1, wherein the endface is acurved surface.
 12. The process for producing a semiconductor deviceaccording to claim 4, wherein the plated barrier layer comprises anickel coating and a gold coating.
 13. The process for producing asemiconductor device according to claim 4, wherein the plated barrierlayer comprises a nickel coating and a palladium coating.